Electromagnetic clutches have been utilized commercially in a variety of applications, including automobiles. Typically, an electromagnetic clutch includes a rotor having an inner annular bearing portion, a clutch portion extending generally radially outwardly from one end of the inner portion and an outer annular portion extending from the clutch portion in a generally overlying spaced relation with respect to the inner portion. The spacing between the inner and outer annular portions receives an electromagnetic coil that may be energized to create a flux field in the rotor. A floating plate mounted to the annular portion may be attracted by the magnetic field for selective coupling to the rotor when the electromagnetic coil is energized.
Another friction clutch has been configured as a normally closed clutch having a number of springs biasedly urging a floating plate into engagement with a friction plate. The entire clutch actuation force is provided by the springs. To disengage the clutch and cease torque transfer from the friction plate to the floating plate, an electromagnet is energized to overcome the force of the biasing springs and translate the floating plate away from the friction plate. While these prior electromagnetic clutches may have served a purpose, a need for improvement exists. In particular, to disengage the floating plate from the friction plate, a relatively large quantity of energy is required to overcome the biasing force of the springs. Accordingly, it may be desirable to provide an energy efficient electro-magnetic clutch.